1. Field of the Invention
The present invention relates to a door unlocking device for a vehicle which unlocks a door locking system when an identification code received from a portable transceiver matches a preset registration code.
2. Related Art
An existing door unlocking device for a vehicle unlocks a door locking mechanism when an identification code received from a portable transceiver matches a present registration code. Such a door unlocking device has the following structure. In short, when the portable transceiver approaches a transmit/receive apparatus mounted on a vehicle, a power signal is transmitted to the portable transceiver from the transmit/receive apparatus. In response to the power signal, the transceiver sends an identification code to the transmit/receive apparatus. When the identification code matches the registration code, the door locking mechanism is unlocked. In this case, the transmit/receive apparatus is designed so as to intermittently send the power signal in order to prevent consumption of a battery, thereby reducing power consumption.
A starter switch for detecting the pulling of the door handle is disposed on the reverse side of an exterior door handle in the vicinity of a driver's seat. When the door handle is pulled to a given position, the starter switch is turned on, so that the transmit/receive apparatus sends the power signal to the transceiver. In response to the power signal, the transceiver returns an identification code to the transmit/receive apparatus.
However, the foregoing door unlocking system suffers from the following problems. More specifically, in the case of the door unlocking system in which the power signal is intermittently sent to the transceiver from the transmit/receive apparatus, the transceiver suspends transmission of the identification code when the power signal is not transmitted; i.e., when the transmit/receive apparatus is in a standby condition. The door cannot be opened at this time, thereby inconveniencing the driver.
In a door unlocking device having a starter switch positioned on the reverse side of the exterior door handle, the starter switch is turned on when a door knob is pulled to a given position, so that an identification code is transmitted. However, it takes a certain amount of time to decode the identification code. If the door knob is pulled up to a position where the door locking mechanism is to be unlocked before the door locking mechanism is released from a locked state, it becomes impossible to open the door and the door becomes disabled, thereby inconveniencing the driver.
More specifically, an existing door unlocking device for a vehicle unlocks a door locking mechanism when an identification code transmitted to a transmit/receive apparatus from a portable transceiver matches a preset registration code. Such a door unlocking device comprises a starter switch positioned on the reverse side of an exterior door handle in the vicinity of the driver's seat.
In such a door unlocking device, when the door knob is actuated to a switching position along the way to a predetermined pivotal location, the starter switch is turned on. A start signal is output to the transmit/receive apparatus from the starter switch to thereby activate the same. The transmit/receive apparatus then transmits a power signal to the transceiver. In response to the power signal, the transceiver sends an identification code to the transmit/receive apparatus. When the identification code matches the registration code, the door locking mechanism is released from a locked state. When the door knob is actuated to a predetermined pivotal position after the door locking mechanism has been released from a locked state, the door locking system is unlocked on condition that the door locking system has already been released from a locked state, thereby allowing the opening of a door.
However, in the case of the door unlocking system having the foregoing configuration, it takes a certain amount of time from after the starter switch has been turned on as a result of actuation of the door knob to the switching position until the identification code is decoded. If the door knob is actuated up to a position where the door locking mechanism is to be unlocked before the door locking mechanism is released from a locked state, it becomes impossible to open the door, thereby inconveniencing the driver.